New Research Suggests Biofuel Blending is Often Inaccurate

Study of Retail Biofuel Samples Suggests National Standards May Be Needed

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February 27, 2008

While sampling blended biodiesel fuels purchased from
small-scale retailers, researchers at the Woods Hole Oceanographic Institution
found that many of the blends do not contain the advertised amount of biofuel.

Marine chemist Chris Reddy and colleagues sampled pure
biodiesel and blends from more than a dozen distributors across the United States.
When testing fuels listed as 20 percent biodiesel (commonly known as B20), they
found that the actual percentage of biofuel ranged from as little as 10 percent
to as much as 74 percent. Only 10 percent of samples met the specifications for
biofuel blends required for vehicles of the U.S. Department of Defense, one of
the leading consumers of the products.

Pure biodiesel (B100) is a chemically prepared mixture of animal
fats and vegetable oils, and it is often used in modified diesel engines.
Biodiesel “blends” combine B100 with traditional petroleum-based fuels in a
manner that allows them to be used in regular diesel engines. Retailers
commonly sell blends that are 20 percent biodiesel (B20) or 5 percent (B5),
while all diesel fuels sold in Minnesota are actually B2 (2 percent biofuel),
in accordance with state standards.

Proponents of such fuels claim that they are more
environmentally friendly because they emit less pollutionsuch as sulfur,
particulates, and hydrocarbonsand may be less toxic for the environment when
spilled.

“Biodiesel is a great product if used properly, and it could
turn out to be an important alternative fuel,” said Reddy, an associate
scientist in the WHOI Department of Marine Chemistry and Geochemistry. “There
is a lot of good feeling about biodiesel, but if we are going to sell it, we
have to make sure what is being sold is accurately prepared. It is a matter of
credibility and consumer confidence.”

Reddy and colleagues happened upon the discrepancy while
studying the potential effects of a biodiesel spill in the marine environment. The
new research was published online on February 27 in the journal Environmental Science and Technology. It
will appear in print in the April issue of the magazine.

Biodiesel blends are often made by local distributors
through simple “splash blending,” whereby ingredients are poured together into
a container in their respective amounts. The intent is that the simple act of
pouring will ensure proper mixing.

But biodiesel is naturally thicker and more viscous than
petroleum-based diesel, so it may be settling into separate layers within fuel
tanks (like a mixture of milk and chocolate syrup, or fruit juice and alcohol).
Reddy and colleagues also pointed to simple human errorpoor math, measurement,
or stirringas a possible reason for the inconsistencies.

Improper blending of biofuels could lead to engine problems
from drivers in cold climates, Reddy noted, because it could freeze or clog
fuel lines. Most auto manufacturers recommend against using mixtures greater
than B20, though the reasons are unclear.

Reddy believes the discrepancies could harm consumer
confidence in the product, which is sometimes sold at a premium price over
traditional petroleum fuels. There could also be financial issues related to taxation
and tax credits for biofuel providers and consumers.

The United
States currently has a voluntary standard
for proper preparation of blended fuels, but no enforcement. The nation does
have an enforceable standard for pure biodiesel.

The new fuel blending research builds on a 2004-2005 study
by the National Renewable Energy Laboratory that suggested some national-scale
manufacturers were having a hard time producing proper blends of biofuel.

Reddy and colleagues worked with WHOI senior scientist Bill
Jenkins and colleagues at the National Ocean Sciences Accelerator Mass
Spectrometer facility to develop an extremely precise radiocarbon-based calibration
method for determining if the balance of biofuels and petroleum is correct. The
new method relies on the fact that petroleum is “radiocarbon dead” (contain no
radiocarbon), while biofuels are enriched with radioisotopes that plants absorb
from Earth’s atmosphere and soil.

The calibration method accounts for the differences in
chemical makeup of different types of oils, such as canola, coconut, soybean,
or animal fats. This method also allows for a direct quantification of the
amount of renewable carbon that is emitted from vehicles, which will aid
researchers in determining the true environmental value of switching to
biofuels.

The Woods Hole Oceanographic Institution is a private,
independent organization in Falmouth,
Mass., dedicated to marine
research, engineering, and higher education. Established in 1930 on a
recommendation from the National
Academy of Sciences, its
primary mission is to understand the oceans and their interaction with the
Earth as a whole, and to communicate a basic understanding of the ocean's role
in the changing global environment.

Chris Reddy, an associate scientist in the WHOI Department of Marine Chemistry and Geochemistry, studies the fate and transport of oil in the environment. (Photo by Bryce Reddy)

The Woods Hole Oceanographic Institution is dedicated to research and education to advance understanding of the ocean and its interaction with the Earth system, and to communicating this understanding for the benefit of society. Learn more »